This invention relates generally to a photographic camera with automatic shutter latch, and more particularly, to a photographic camera having a shutter latch automatically releasable by a shutter drive mechanism and automatically relatched by means of a film advance mechanism.
Electrically driven exposure control systems are advantageous in that they minimize operator requirements of shutter recocking, etc. and are particularly suited for electronic control. For conservation of power, such systems require provision of a stable deenergized shutter condition when the camera is not undergoing exposure operations. An exemplary system of this type is described in U.S. Pat. No. 3,820,128 issued to J. T. Burgarella, et al. on June 25, 1974 wherein a compact, automated single lens reflex camera is described, and which includes a shutter diaphragm system having shutter blades mechanically biased to an open (viewing) position and electrically biased to a closed position. Advantageously, the exposure system of the above-noted patent is electrically sequenced to provide a precise control over the exposure operation. That is, both the initiation and termination of the exposure interval are electrically, rather than mechanically, determined and, accordingly, may be precisely controlled. However, while the system is particularly adapted for through the lens viewing and provides a normally open shutter, it can be understood that it would also be desirable to provide a normally closed arrangement without compromising the system advantages.
Toward this end, there is described in a copending application for U.S. Pat. application Ser. No. 554,777 entitled "Photographic Apparatus With Sequencing System", by B. Johnson and G. Whiteside, filed Mar. 3, 1975, a latching mechanism provided in order to maintain the shutter blade mechanism in its light blocking position without having to maintain a solenoid in its energy consuming energized state. The means described in the aforementioned patent application for latching and unlatching the shutter blade mechanism comprises a forwardly extending finger arranged for reciprocal movement in correspondence with a film advancing mechanism. The finger is adapted to extend into the locus of movement of the blade mechanism when the film advance mechanism is in its forwardmost position. The shutter blade elements are of the so-called "scanning type" embodying a pivotal walking beam whereby the forward end of the finger provides a rearwardly movable stop, in the path of travel, against which the lower end of the walking beam abuts to prevent clockwise rotation of the walking beam under the influence of a biasing spring. The shutter blade mechanism is unlatched in response to the predetermined rotation of the sequencing gear which causes the film advance mechanism and its associated finger latch to move rearwardly under the influence of another biasing spring. This rearward movement retracts the finger from the path of travel of the walking beam thereby permitting rotation of the beam about its pivot towards the shutter open position. During the course of the cycle of camera operation, the film advance mechanism again moves forwardly to cause the finger to extend through the locus of rotation of the walking beam to relatch the shutter thereby allowing the solenoid to be deenergized.
Another exposure control system utilizing electrically controlled shutter blade elements employing a latch for holding the blades in a light blocking position is more fully described in a copending application for U.S. patent application Ser. No. 608,663, entitled "Electro-Mechanical Shutter System Having Mechanical Latch", by L. Douglas, filed Aug. 8, 1975. In accordance with the general concept of the aforementioned invention, the exposure control system includes a reliable shutter latching arrangement which requires shutter actuation for release. Thus, the exposure control system includes a shutter latch released in response to combined electrical and mechanical actuation of the exposure control system. A mechanical shutter latch arrangement is unlocked just before or simultaneously with energization of the exposure control system and then subsequently released in response to initial shutter blade movement resulting from energization of the electrical drive element. However, while the aforementioned shutter latch arrangements are perfectly suitable for their intended purposes, it can be understood that other operational and size constraints make it desirable to provide an automatic shutter latch mechanism meeting the following objectives.
Therefore, it is a primary object of this invention to provide an automatic shutter latch mechanism which may be released in response to initial shutter blade movement resulting from energization of the shutter drive means and which may thereafter be moved into position to relatch the shutter blades in response to film advancement.
It is a further object of this invention to provide an automatic shutter latch mechanism responsive to initial shutter blade movement resulting from manually actuated energization of the electrical shutter drive means for unlatching the shutter blades while simultaneously actuating a power interlock switch to maintain the electrical energization of a photographic exposure control system after the manual deactuation thereof by the user.
It is a further object of this invention to provide an automatic shutter latch mechanism which is responsive to initial shutter blade movement resulting from energization of the electrical shutter drive means for releasing the shutter blade mechanism together with a shock damping arrangement to inhibit the accidental unlatching of the shutter blade mechanism resulting from shutter blade movement occassioned through extraneous vibrations, sudden shock or otherwise.
Other objects of the invention will in part be obvious and will in part appear hereinafter.